In vivo imaging platform for DM1 drug discovery - PROJECT ABSTRACT/SUMMARY Myotonic dystrophy type 1 (DM1) is a multisystemic disorder caused by CUG repeat expansion in the 3’ UTR of the DMPK gene. DM1 patients can have between 50 to 5,000 CUG repeats, leading to DMPK mRNA aggregation within the nucleus. These ribonuclear clusters, termed foci, sequester several splicing factors, such as muscleblind-like (MBNL) proteins, and transcription factors, leading to dysregulation of splicing, miRNA and circRNA formation, and mRNA location and stability. DM1 is the most common adult form of muscular dystrophy and affects 1 in 8,000 people worldwide. There is currently no cure for DM1 and treatment consists of symptom management. Recent advances in RNA-focused drug library design and screening tools now allow better, more biologically relevant hit screening that overcome traditional protein-based drug discovery approaches. However, appropriate animal models for efficient preclinical testing of RNA-focused drug candidates remained lacking. Pharmacokinetic and target engagement studies for every new drug candidate still rely on biochemical measurements in harvested tissues, which is expensive, time consuming, and requires large numbers of animal sacrifice. There is currently no in vivo model capable of monitoring toxic foci and MBNL sequestration, the trigger of DM1 disease phenotype, in real time high-throughput format, and in a non-invasive manner to limit the number of animals needed. The goal of this SBIR Phase I project to develop an in vivo reporter platform that allows more efficient evaluation of triaged drugs and lead compounds for target engagement and other PK metrics. We will use our proprietary fluorogenic RNA aptamer technology to develop in vivo reporters that can detect drug-induced changes in toxic foci formation and CUG-MBNL interaction. In Phase, I we will demonstrate the feasibility of the in vivo reporter system in DM1 model cell lines and animal model and in Phase II, we will generate transgenic reporter animals, perform preclinical testing with collaborator lead compounds, and expand the platform capability toward other microsatellite diseases.
